The Supreme Court on Monday put some limits on the Environmental Protection Agency's landmark 2011 regulations aimed at cutting emissions of greenhouse gases from stationary sources like factories. But seven justices agreed to leave the vast majority of the far-reaching program intact, thereby leaving the path toward new emissions regulations unimpeded.

The decision is noteworthy for reaching a compromise between striking down the EPA's global warming program, which is a cornerstone of the Obama administration's plan to meet domestic and international climate goals, and upholding it entirely.

First, this decision does not affect the proposed greenhouse gas emissions cuts from existing power plants that the Obama administration rolled out on June 2. Instead, it deals with prior regulations issued for new motor vehicles and some stationary sources, like factories and power plants.

In addition, the decision in this case only slightly undercuts the EPA's existing greenhouse gas emissions regulations, leaving the majority of the existing programs intact.

Now for the nitty-gritty details:

The case, Utility Air Regulatory Group v. EPA, centers on how the EPA applied the 1970 Clean Air Act's provisions when it moved in 2011 to control greenhouse gas emissions from stationary and mobile sources, such as power plants and vehicles. The majority of the court held that the agency had overstepped its bounds in how it interpreted the Clean Air Act, saying that it had essentially rewritten the law.

The majority decision, written by conservative Justice Antonin Scalia, affirmed the agency's right to regulate greenhouse gases under the Clean Air Act, something the Supreme Court itself had cleared a path for in Massachusetts v. EPA in 2007, but held that the EPA went too far in how it shaped its rule.

The EPA had argued that were it to implement the Clean Air Act exactly as it was written, it would mean that tens of thousands of small emitters, including homes and small businesses, would be subject to emissions limits. To avoid this massive expansion in the agency's reach across the U.S. economy, the EPA decided to apply the greenhouse gas limits under the Clean Air Act only to larger stationary sources, essentially redefining part of the act.

The agency did this through a so-called tailoring rule that set a new emissions threshold that would trigger greenhouse gas emissions regulations from facilities not already subject to regulation under the Clean Air Act.

The Clean Air Act requires permits for sources that have the potential to emit more than 100 to 250 tons of a given pollutant per year, but the tailoring rule that the EPA wrote set a new threshold of 100,000 tons per year for greenhouse gases. The court rejected this change, as Scalia wrote that only Congress can change the threshold:

"In the Tailoring Rule, EPA asserts newfound authority to regulate millions of small sources—including retail stores, offices, apartment buildings, shopping centers, schools, and churches—and to decide, on an ongoing basis and without regard for the thresholds prescribed by Congress, how many of those sources to regulate. We are not willing to stand on the dock and wave goodbye as EPA embarks on this multiyear voyage of discovery."

This part of the decision was backed by a 5-to-4 vote that overturned an appeals court decision, with the court's four liberal justices dissenting. They argued that the EPA's tailoring rule was a reasonable action taken to avoid overly burdensome and far-reaching regulations.

Global average surface temperature departures from average during May, 2014. Increasing amounts of greenhouse gases in the air are causing global warming.

Image: NOAA

But here's the really important part: By a 7-to-2 vote, the court allowed the EPA to regulate greenhouse gases from sources that would already need permits based on their emissions of conventional pollutants. These sources represent the vast majority of facilities that are covered by the regulations. This part of the opinion drew support from the court's four liberal justices, as well as Scalia, Chief Justice John Roberts and Justice Anthony Kennedy.

As a result, the EPA will be permitted to regulate pollution sources that account for 83% of the greenhouse gases coming from stationary sources in the U.S., a slight reduction from the 86% that would have been regulated had the court upheld the entirety of the regulations.

The EPA issued a statement that called the decision a "win."

“Today, the Supreme Court largely upheld EPA’s approach to focusing Clean Air Act permits on only the largest stationary sources of greenhouse gases such as power plants, refineries, and other types of industrial facilities,” the EPA said. “The Supreme Court’s decision is a win for our efforts to reduce carbon pollution because it allows EPA, states and other permitting authorities to continue to require carbon pollution limits in permits for the largest pollution sources."

Outside observers said the court succeeded in finding a compromise that provided a small victory to the utility companies that oppose the regulations, while also giving the rules' supporters a victory as well.

“Scalia split the baby, allowing EPA to regulate big operations but preventing a great expansion in EPA authority that nobody truly wanted," said Tim Profeta, president of the Nicholas Institute for Environmental Policy Solutions at Duke University, in a statement.

Robert B. McKinstry Jr., a partner at Ballard Spahr LLP in Philadelphia, told Mashable in an interview that the decision won't hamstring the EPA's ability to rein in emissions that are causing global warming. “In terms of what the EPA is doing, the impact of this decision is I would say very little,” he says. “EPA’s program, in this decision, emerges intact.”

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